With regard to the first major embodiment of the present invention, latex polymers are utilized in a variety of products due to the unique features of their delivery system. Latex polymers, by nature, have lower viscosities than their solution counterparts. This lower viscosity allows for higher polymer concentrations to be delivered in an application without encountering the numerous problems associated with high viscosity fluids. The reason for the unique viscosity behavior of latex polymers results from the heterogeneity of the system. The fact that the latex polymers are dispersed, rather than dissolved, in a continuous low viscosity medium reduces the influence of the latex polymer on the viscosity of the media. Therefore, the continuous phase or solvent of the latex is the dominant component affecting the viscosity of the system.
Typically, the continuous phase of most commercial latexes is water. This is beneficial in that water has low toxicity and is not flammable. Water is a good choice when the continuous phase is to be used as a delivery system for the polymer. In some circumstances, however, water may be detrimental to the substrate, or it may be necessary to change the drying characteristics of the latex.
Solvents other than water may be used in the continuous phase. For example, the addition of diol solvents in minor amounts is known. JP 04335002 teaches the addition of alcohol(s) as an antifreeze agent for the production of vinyl ester emulsions at low temperatures. The amount of the diol solvent disclosed is below 50 wt. %. JP 63186703 teaches the addition of film forming agents and plasticizers in an amount up to 10 wt. % of the solid component to effect film formation properties of the resulting emulsion. JP06184217 teaches the addition of polyols and water-soluble inorganic salts to vinyl chloride suspension polymerizations to produce vinyl chloride polymers that have good powder fluidity. EP 255137 teaches the use of water soluble alcohol in a water/alcohol level of 100/0 to 50/50 for producing polyvinylester with a high degree of polymerization.
U.S. Pat. No. 3,779,969 describes the use of propylene diol or diethylene diol in amounts of 10-50 wt % of the emulsion. The ethylene diol is added to impart improved wetting properties to the emulsion.
U.S. Pat. No. 4,458,050 describes a process for the manufacture of polymer dispersions in diol chain extenders. The patent relates to the production of polymers which have low viscosity for the preparation of polyurethanes. The '050 patent does not teach compositions which result in stabilized latexes in diol solvents. The patent also teaches large amounts of polymeric stabilizers to produce the dispersion polymer.
JP 60040182 and JP 64001786 teach compositions for water-oil repellency for fabric treatment. The compositions are aimed at producing fluoropolymer emulsions in a mixture of diol solvents. Such fluoropolymers are not the subject of this invention.
U.S. Pat. No. 4,810,763 teaches suspension polymerization in an organic medium for the preparation of pressure sensitive adhesives. The compositions described in the '763 patent are specifically aimed at producing large particle size dispersions. This patent does not disclose compositions which size latexes having a particle size below 1000 nm. This reference also does not disclose emulsion polymerization.
U.S. Pat. Nos. 4,885,350 and 5,061,766 teach the dispersion polymerization of vinyl monomers in hydrophilic organic liquids. To produce the dispersion polymer, large amounts of polymeric dispersion stabilizers are taught.
Prior to the present invention, it had not been previously known to utilize 40%, more preferably 60% or greater, of diol, by weight of the continuous phase, in the continuous phase of a latex polymer. This amount of diol has been found in the invention herein to provide certain advantages in a latex composition, such as improved compatibility with a particular substrate, better drying characteristics of the latex, or it can be used in the second major embodiment of the invention (production of a condensation polymer/first polymer matrix).
With regard to the second major embodiment of the present invention, it is known to modify condensation polymers by blending the condensation polymer with another polymer in an extruder. For example, to improve the impact properties of a polyester, a low Tg elastomer is typically added to the polyester in a twin-screw extruder. Japan Kokai JP 02155944 describes compounds for moldings comprising physical blends of saturated polyester with polystyrene polymers containing 1-100 phr glycidylamido-grafted olefin polymers of glycidyl methacrylate-graft olefin polymers. Jpn. Kokai JP 02016145, JP 02024346, JP 01123854, JP 01153249 and JP 01163254 each teach the blending of aromatic polyesters with resins prepared by graft emulsion copolymerization. In each of these references, the size of the dispersed phase is said to be critical in obtaining good properties. However, this is an energy intensive process, sometimes resulting in an undesirable reduction in the physical properties of the polymer, in particular the molecular weight. Further, a blending step is required, which utilizes more resources and more time.
U.S. Pat. Nos. 5,652,306, 4,180,494 and 5,409,967 disclose compositions for impact modification of aromatic polyesters that involve blending an acrylic or polybutadiene/acrylic rubber powder with polylethylene terephthalate (PET). The acrylic rubber particles are prepared by typical core/shell emulsion polymerization and then harvested by spray drying the latex. The procedure for latex harvesting is outlined in U.S. Pat. No. 3,895,703.
The extrusion blending of an elastomer and a plastic is labor intensive and time consuming. Typically, polybutadiene or poly(butyl acrylate) are used as the low Tg (glass transition temperature) polymer to impact modify the polyester. These low Tg elastomers are difficult to handle and require that a second monomer, typically poly(methyl methacrylate) be utilized as a shell surrounding the low Tg polymer core so that the low Tg polymer may be handled. The core-shell polymer is isolated, dried and then added to the polyester in an extruder.
There exists a need for a process for producing a polymer blend by more economical methods. It would also be desirable be able to utilize both core shell and/or non core shell polymers in a process for producing a polymer blend, again, in an economical fashion. Further, it would be desirable to utilize novel polymer sources, for example glycolyzed polymers, for producing a polymer blend. Also, it would be desirable to utilize reinforcing agents, e.g., glass fibers, to improve the physical properties of the resulting polymer blends. Moreover, it would be desirable to modify the characteristics of the polymer blends of the present invention by utilizing a buffered system. Still further, it would be desirable to obtain thermoplastic elastomeric materials according to the present invention. Such needs have been satisifed by the present invention, which can achieve such polymer blends in a polymerization reactor, wherein the physical properties of the resulting condensation polymers are maintained or improved. Still further, latex polymer compositions of improved properties are also provided.